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UNIVERSITY OF ILLINOIS 


Agricultural Experiment Station. 


URBANA, FEBRUARY, 1902. 


BULLETIN No 60. 


APPLE ROTS IN ILLINOIS. 


By GEORGE P. CLINTON, M.S., AssIsTANT BOTANIST, 
AGRICULTURAL EXPERIMENT STATION. 


During the past few years considerable complaint has been 
made in this state of the loss of apples through rotting. The 
trouble has been attributed chiefly to the bitter rot fungus which, 
apparently, has been unusually injurious in the United States and 
especially in certain parts of the Mississippi Valley during this 
period. Beginning the past season the Experiment Station has 
undertaken an especial study of this and other apple rots of Illinois 
both in the field with reference to their distribution, damage, and 
prevention and in the laboratory with reference to the life history 
of the fungi that cause them. This bulletin includes the studies, 
especially of the bitter rot fungus, made from the latter point of 
view during the months of July, August, and September. 

Bitter rot, while the chief, is not the only serious rot of-apples 
in Illinois. A superficial study only has been made of these other 
rots, the most common of which are briefly mentioned here. 

189 


190 BULLETIN NO. 69. (February, 


Fruit Burn. As indicated by the name this is a scalding of 
apples due to the sun’s heat. Ordinarily this trouble is confined 
to the fruit after it has fallen to the ground, though during the 
past unfavorable apple season there has been some complaint of 
the fruit burning on the trees: The apples as they lie on the 
ground begin to scorch on the south or sunny side and the brown 
discoloration gradually increases in size both by spreading over 
the surface and by extending inward, eventually forming a sort of 
baked apple. In its earlier stage diseased tissue taken from the 
interior of such apples for cultural examination gives no growth of 
bacteria or fungi, but in time, no doubt, these agents often aid in 

the destruction of the tissues. The trouble, apparently, is not a 
very serious one. Plate A, Fig. 1, shows an apple affected with 
fruit burn in its earlier stage. 

Brown Rot, Monilia fructigena, Pers. This rot was not seen 
very often the past season, though in some years it appears as a 
rather common cause of the rotting of summer varieties. It soon 

_ produces a complete rotting of the infected apples which turn 
a brown color and show the presence of the fungus by the 
breaking out of small, greyish, dense pustules of spore bearing 
mycelium. These fruiting sori are usually found only when the 
fruit is in a moist place, especially when it has fallen on the damp 
earth, though they are sometimes seen on apples hanging on the 
tree. Ordinarily this rot appears only on ripening summer varie- 
ties and most commonly after they have fallen from the tree. The | 
same fungus also causes the common rotting of peaches, plums, 
and the occasional rotting of cherries, etc., and on some of these 
hosts often causes serious loss. 

_ Sorr Rot, /hizopus nigricans, Ehr. ‘This rot does not com- 
monly attack apples on the trees though it was so found in a fruit- 
ing condition the past season on ripe summer varieties. It is a 
rather soft rot which is not otherwise very characteristic unless, as 
rarely happens except under moist conditions, the fungus breaks 
out on the surface in its fruiting stage, which consists of short, 
somewhat bunched threads bearing on their ends the small black 
spore cases, The fungus is primarily more of asaprophytic than a 
parasitic fungus and is a common cause of the rotting of various 
mature vegetables and fruits, Rots like those shown in Plate A, 
Fig. 2, are sometimes caused by this fungus. 

Fruit Birorcu, Phyllosticta, sp. What appears to be an un- 
described fungous trouble of apples was first found by Professor 
Burrill during July of the past season in a number of places in 
southern Illinois. Later it was seen by the writer on a single 


1902.] “APPLE ROTS IN ILLINOIS. IgI 


variety in the University orchard and it has been reported since by 
various persons as common on certain varieties in different parts of 
southern Illinois. Mr. A. A. Hinkley, of DuBois, reported it as a 
common trouble in his orchard during the past season and also 
stated that he had known it for some time but had been calling it 
scab. It has. been found on Rambo, Ben Davis; Janet, Grimes’ 
Golden, and Winesap and undoubtedly eccurs on other varieties. So 
far as reported Rambo and Ben Davis were the worst affected of 
these. 

The trouble appears at first as small dark colored blotches of 
quite irregular shape that are more or less scattered over the surface 
of the apples and quite superficial, On these are often seen quite 
small pustules which are the conceptacles containing the spores, 


which are hyaline, oval to subspherical and chiefly 7--10 vin greatest - 


diameter. They germinate rather readily when placed ina drop 
of water, sending out short, septate germ-threads. Later in the 
season, September to October, the disease assumed a more serious 
aspect. The discolored spots became enlarged and more or less 
merged into extended and often slightly sunken areas and the dis- 
eased tissue extended inward so that in some cases the whole apple 
was affected with dry rot. This later injury may possibly in part 
have resulted from the action of some other fungi or bacteria. 
Plate B,. Fig. la—b, shows action of the fungus in its earlier and (c) 
in its later stage. 4 


Cultures made by taking diseased tissues from the interior of 


affected apples produced a characteristic dark olive green mycelium 
that formed patches of rather slow growth on the medium and had 
not after two months’ development given any sign of the formation 
of a spore stage. 

Being unable to identify the species of this fungus, specimens 
were sent to the veteran mycologist, J. B. Ellis, for inspection and 
‘he suggested the possibility of its being the fructigenous form of 
Peck’s Phyllosticta limitata. Specimens were then sent to Peck 
who reported the two as distinct. This view was confirmed by the 
examination of specimens from the material from which Peck de- 


scribed Phyllosticta limitata, Mr. A. F. Stewart kindly furnishing ) 


these. This fungus is also distinct from Phyllosticta pirina, Sacc. 
and Phyllosticta prunicola (Opiz..) Sacc., which have been reported 
on Pirus. So far as can be ascertained thefungus seems to be a 
new species and it is hoped to make further investigation of it the 
coming year. 

During the latter part of the season when one might expect 
the fruiting pustules to form spores more abundantly it was diffi- 


192 BULLETIN NO. 69. [ February, 


cult to find any containing spores, but instead their contents were 
usually in an immaturecondition. This suggested that the fungus 
was beginning the development of its permanent or ascosporic 
stage, and it is possible this may be found eventually. 


Biack Rot, Spheropsis Malorum, Berk. This fungus has 
been known to occur in Illinois at least since 1879 when Professor 
French of Carbondale sent specimens of rotting apples to State 
Botanist Peck of New York who so identified the fungus found on 
them. Black rot causes more or less decay of apples everywhere, 
and it has been a matter of some interest in the state to know how 
much of the damage here is to be attributed to this source and how 
much to bitter rot. The observations of the past season show the 
latter to be the much more aggressive fungus, though it does not 
have the wide distribution of the former, which is likely to occur 
to some extent in every orchard. On green apples black rot usual- 
ly appears only where they have been injured in some manner, as 
by worms, etc,, and is most commonly found on windfalls. Ordi- 
narily it does little damage to perfect, green fruit on the trees but 
sometimes on ripe summer and crab apples does more or less dam- 
age, as was found in a few cases the past summer. It is also one 
of the chief causes of the rotting found in market apples. 


Black rot is so called because of the color assumed by the in- 
fected fruit. Often at first the rotten part is brown but in time 
this becomes black. The color is due to the mycelium of the 
fungus which while at first hyaline eventually becomes dark olive, 
especially at the surface of the fruit. The mycelium occurs rather 
abundantly through the rotten tissue and is made up of septate 
threads often quite irregular and of considerable size. The rotting 
is usually well along before the fruiting stage appears as abundant 
but very small black pustules at the surface of the apple. These 
pustules are roundish conceptacles having the outer wall made up 
of black or often purplish tinged cells and containing the spores. 
The spores often ooze out from the conceptacles in small white 
tendrils. Whileat first they are colorless and simple, they even- 
tually become deeply colored and usually uniseptate. As the rot- 
ting advances the apples become shriveled so that finally they form 
small, hard, irregular mummies. Plate B, Fig. 2a—d, shows some- 
thing of these progressive stages. 

The black rot fungus also occurs on the leaves and branches and 
on these parts seems to cause more serious damage than on the green 
fruit. On the leaves the brownish spots produced are much like 
those of the leaf spots or Phyllostictz fungi but are apt to be more 
irregular and larger. Ordinarily the fruiting pustules are not borne 


1902. ] APPLE ROTS IN ILLINOIS. 193 


very abundantly on these spots. The old dead twigs so often found 
on unpruned apple trees usually bear an abundance of the fruiting 
pustules and while formerly it was believed that the fungus grew 
on these only as a saprophyte there is now evidence that it is often 
responsible for the death of such twigs. 

Black rot is also a fungous trouble of other of the pomaceous 
fruits. The fact that it occurs on these different hosts and on dif- 
ferent parts of the same host has such differences in general ap- 
pearance, together with the fact that specimens show considerable 
difference in color and septation of spores according to their age, 
has caused botanists to describe. this fungus under a number of dif- 
ferent names. ; 

MISCELLANEOUS Rots. Besides the preceding and the bitter rot, 
there are a number of other fungi, also bacteria and yeasts, that 
have been found in rotting market apples. Sometimes these are 
the primary agents-of the rotting and sometimes only secondary 
ones. In a cultural examination of tissue taken with the usual 
precautions from the interior of apples at the juncture of healthy 
and rotten areas the following results were obtained with twenty- 
three samples gathered from different grocery stores in Champaign 
and Urbana: Four developed ehizopus nigricans, soft rot; four, 
Spheropsis Malorum, black rot; five, nothing ; four, bacteria or 
yeasts or both; one, Glzocladium penicillioides; one Phyllosticta 
sp., fruit blotch; three, mixtures of various fungi or non-fruiting 
forms; one, Aspergillus sp. These cultures were each made in 
duplicate and usually both gave the same result, thus showing that 
the primary cause of the rotting was usually one agent, though no 
doubt in the older rotten parts it was often assisted by other forms. 

Besides the above species there were also found on badly rotted 
apples several other fungi that apparently occurred there primarily 
as saprophytes, no doubt often to the detriment of the primary form 
causing the rotting. Such forms were species of the following 
genera: Cephalothecium, Penicillium, Aspergillus, Mycogone, 
Alternaria, and Acremoniella. 


Brrrer Ror. 


OccurRRENCE. None of the preceding fungi compare with the 
bitter rot fungus in the damage that it may cause to the apple crop, 
since it is a parasite that is equally at home on the green or the ripe 
fruit. It also has a wide distribution over the world. It seems to 
have periods of greater and lesser destructiveness and especially 
during the past two or three years has developed more vigorous in 
southern IHinois. While no attention has been paid to it by the 


194 BULLETIN NO. 69. [ February 


Station until recently, it has been known to exist in southern 
Illinois at least since 1869. During the past two years it has been 
found in a number of places in this part of the state, the most 
northern reported limit being at Urbana. It seems quite probable 
that it occurs, at least sparingly, in central and northern [llinois,- 
as it has been found as far north as Maine. The general informa- 
tion now at hand, however, indicates that it is a more active agent 
in regions with a climate like southern Illinois. 

DamaGE. Something of the damage that has been caused in 
this state is shown by the following statement of Mr. C. H. Murray 
of Clay City in the transactions of the Illinois Horticultural Society 
for 1870, page 346. Mr, Murray says concerning an orchard of a 
Mr. Finch: ‘‘ Last year it had at least one thousand bushels of ap- 
ples on and the proprietor did not get a bushel of winter apples. 
The bitter rot blasts them like the breath of ruin and the promise 
of spring ends in disappointment and decay. Many experiments 
have been tried to arrest this evil but so far none of them has proved 
efficacious. * * * * * For ten or eleven years it gave the 
most bounteous returns and produced wagon loads of the finest 
fruit. It then began to decline. The fruit commenced to-speck 
and the evil increased until the trees are little more than an incum- 
branceonthe ground. * * * ‘The Vandevers all have the ‘bitter 
rot’ also the Bellflowers but the Pippins and Summer Queen have 
not, but have asweet or summer rot.” The interest manifested by or- 
chardists in southern Iifinois the past two seasons shows that bitter 
rot is still a pest that is greatly feared and for sufficient reason, 
since in some orchards the entire crop has been destroyed by it. 

PREVENTION. This being so serious a trouble naturally at- 
tempts have been made to prevent it. More or less success has 
been reported by different experimenters. Some have advocated 
picking the infected fruit. This to be of any service must be very 
thorough and commenced with the very first appearance of the rot 
and repeated often. Old bitter rot apples lying on the ground or 
mummies attached to the tree are apparently the source of infec- 
tion the coming year, and these especially should be destroyed. 

Spraying has been tried with more or less success. To be of 
value it should be commenced before the first appearance of the rot 
and repeated from time to time until danger is past. It is espe- 
cially important that it be repeated after each rainfall. The Hor- 
ticultural Department of the Station is at work along this phase of 
- the question and whatever results are obtained will be reported. 

APPEARANCE OF INFECTED FRUIT. Sometimes apples begin to 
rot at numerous points scattered over their surfaces, as is shown in 


1902. ] APPLE ROTS IN ILLINOIS. 195 


Fig. 1, Plate C. More commonly the infection starts at one or a 
few places, as is shown in (a) and (b) Fig. 2, Plate C. The char- 
acter of the rot varies somewhat with the variety infected and the 
weather conditions, but in general the original small point of in- 
fection increases to a brown rotten area a quarter to a half an inch 
in diameter without showing external growths of any kind. About 
this time, however, numerous, small, covered, usually black pus- 
tules appear at the center. These are the fruiting sori and if the 
conditions are favorable they soon rupture the covering cuticle and 
- ooze out on the surface small pinkish masses of agglutinated spores. 
If the variety offers too great resistance to the fungus or if the 
weather conditions have been unfavorable—that is, too dry—the 
fruiting pustules may continue to be formed but with few or no 
spores oozing out. The sori follow rather closely the circumfer- 
ence of the rotting area and usually develop in rather distinct con- 
centric circles. 

The diseased tissue is separated quite sharply from the healthy. 
At the same time that the rotting is developing outwardly it is 
also progressing inwardly about as rapidly and a cross section of 
the apple shows the rot deepest over the center and narrowing 
from this to the border where it may be quite shallow. The rotting 
progresses rapidly and there is usually skrinking of the tissues so 
‘that the center is more or less depressed. Another peculiarity of 
the rotten part is its bitter taste, hence the common name of bitter 
rot. Sometimes other agents aid in the rotting but ordinarily in the 
fruit attached to the tree the decay is due entirely to the bitter rot 
fungus. The characteristic appearance of an apple after bitter rot 
has made considerable headway is shown in Plate C, Fig. 2c. In 
this case the spores have oozed out in numerous small globules 
arranged in concentric circles and have become dried up. 

CONDITIONS AFFECTING DEVELOPMENT, etc. The effect of 
moisture on the production of spores was shown in some of the ino- 
culation experiments. Inoculated apples kept unprotected in the 
air of a room produced numerous fruiting sori but these remained 
as unruptured black pustules, while similar apples surrounded bya 
moist atmosphere, by placing them under small bell jars, pro- 
duced fruiting pustules that oozed out abundant spores in the char- 
acteristic pinkish masses. These conditions are illustrated in (c) 
and (b) of Fig. 2, Plate D. Bitter rot apples that are kept under 
moist conditions as they become old change the color of the sori to 
quite dark olive; also under such conditions, especially if the skin 
of the apple has been ruptured, a growth of dirty olive mycelium 
is likely to spread over the surface, Plate H. Fig. 1c. These latter 


Pag tS Nae gs Ae 8 of NS jae Pa eee eee as ST 
ba uy : 1K af oo a sr 


196 BULLETIN NO. 60. [ February, 


however, are conditions that are not seen on fruit while attached 
to the tree. 

Bitter rot develops rather fast from the first. The rate of de- 
velopment is undoubtedly affected somewhat by the variety 
attacked. The difference in development -on a very unfavorable 
and on a favorable variety is shown in Plate F; Fig. la, showing 
the unfavorable variety fifteen days after and Fig. 2a or b the 
favorable variety ten days after inoculation. The state of matur- 
ity possibly may have some influence on the rate of rotting though 
ordinarily the rotting begins in the green apples. Apparently 
sound ripe apples that were brought in a trunk from southern 
Illinois when examined four days later showed rotten areas one 
quarter to one half of an inch in diameter. In the inoculation ex- 
periments, rotten areas one to two inches in diameter were pro- 
duced inside of ten days. Moisture does not seem to increase the 
rate cf rotting though as stated before it affects the character of 
‘spore production. In fact the apples kept inthe dry air apparently 
rotted as fast, if not faster, than those left under more moist con- 
ditions, Plate H, Fig. 1 a—c, shows the development, during ten 
days, of rot on apples kept under different conditions of moisture, 
(a) being kept in open air, (b) under a bell jar, and (c) undera 
bell jar with moisture. 

SPECIES AND VARIETIES INFECTED. Bitter rot has been re- 
ported in Illinois only on the apple though it is known to occur 
elsewhere on the pear, peach, quince, and grape. It was produced 
however, on these hosts in the laboratory inoculation experiments, 
except in the case of the quince where only one, a very green speci- 
men, was inoculated. While capable of growing on a great variety 
of apples it seems to have a preference for certain kinds. Ben 
_ Davis and Grimes’ Golden which are favorite varieties in southern 
Illinois are among those that are severely attacked. 

That the fungus is much severer on certain varieties was shown 
in an orchard near Urbana. In this case two trees of the same 
variety were so badly infected that all of their apples were de- 
_ stroyed. Other varieties immediately surrounding them and whose 
branches even interlaced escaped with a slow rotting of a few ap- 
ples, and the other trees of the orchard showed no bitter rot what- 
ever...; :, 

MANNER OF INFECTION. Rot generally makes its appearance 
in July and whether it causes considerable or little damage seems to 
depend largely on the amount of wet weather during the remainder 
of the season. As has been shown the spores ooze out of the sori 
much more vigorously under moist conditions, hence in rainy 


1902. ] : APPLE ROTS IN ILLINOIS. 197 


weather there is undoubtedly furnished a greater supply of these 
spores for infection, and at the same time increased moisture on the 
apples favors germination of such of the spores as have been carried 
to them. 

How are the spores carried from the diseased to the sound fruit 
to produce infection? They are never of a dusty nature so the 
wind would not be of much aid in their dispersion. When dry 
they are more or less glued together and when moist form a some- 
what sticky mass. It is quite probable that during rains many of 
the spores are washed over the surface of diseased apples or even 
carried to the healthy ones, Rain, however, is an agent that 
would be of little or no use in carrying spores from one tree to 
another. 

It is undoubtedly true that insects are one of the chief agents 
of dispersal, especially the small pomaceous flies of the genus 
Drosophila. These flies are produced very abundantly in bitter 
rot apples under such conditions of moisture as are favorable for 
the production of spores. That they can serve as dispersing agents 
was shown in an experiment where some of them were confined in 
a moist chamber containing bitter rot and sound apples, the latter 
being sprayed a number of times with water. Ina short time the © 
characteristic bitter rot areas appeared scattered over the surface 
of the sound.apples. The appearance of the apple shown in Plate 
C. Fig. I, indicates that flies may have been the infecting agents im 
this case. This apple was gathered soon after WPAN 8 rains at & 
time when bitter rot was common. 

Lire History. The life history of the fungus so far as de- 
termined is as follows: The bitter rot begins to appear upon the 
green fruit about July and gradually spreads, the spreading and 
consequent damage depending upon the character of the weather. ° 
Apples often keep rotting for the remainder of the season and even 
after they are stored in the fall, During this parasitic stage the 
only spore form is the summer or Gleosporium one developed as 
the pinkish pustules so abundant on the rotten areas under favor- 
able conditions. Being thin walled and unprotected such spores 
are not adapted to live over the winter and ina the disease the 
next summer. 

However, in the fall and succeeding spring on the mummy 
apples, the fungus, as a saprophyte, gives rise to the permanent or 
Gnomoniopsis spore stage. The Gleosporium spores that have not 
been carried away disappear through germination and more or less 
of a mat of fungus threads covers the apple. Protected by this, 
perithecia that develop asci with ascospores, which evidently come 


“- e, 
4 


a AS a. REP hia RPS saa * nti ny By ills 


198 BULLETIN NO. 69. [February, 


to maturity the next summer, are gradually developed in a stroma. 
These ascospores are shed out of the asci and perithecia when ma- 
ture and are then scarcely to be distinguished from the Gleospor- 
ium spores. No doubt they are carried by the pomaceous flies to 
the green apples and thus start the disease again for another year, 
So far it has not been discovered that the fungus grows on the 
twigs and by this means carries the fungus over the winter. Very 
often the infected apples are entirely rotted on the tree and the 
mycelium can be found somewhat in the fruit stems but no evi- 
dence was found that it passed through these into the tissues of 
the twigs atid succeeded in establishing itself there. A more de- 
tailed account of the two stages of the fungus is given as follows: 


SUMMER OR GLEOSPORIUM STAGE. 


SPORES, SORI, AND MYCELIUM. This is the stage that is para- 
sitic and so is the one that is commonly seen. As explained be- 
fore, the fruiting pustules are produced near the surface and under 
favorable conditions ooze out on the surface innumerable spores to 
form small pinkish masses. When produced under quite moist 
conditions these spore masses are quite viscid and hence adapted 
to be carried by insects that come in contact with them in their 
search for food. The pink color may possibly serve as a means 
for attracting insects. 

As seen under the microscope the spores are colorless. They 
are typically oblong with rounded ends, but are occasionally 
slightly curved. They vary in shape, however, from ovate to nar- 
rowly oblong and may occasionally have one end pointed. At their 
center and usually to one side, a hyaline area is to be seen, and, 
while normally the spores are simple, a septum is often formed 
here at the time of germination. When first formed the spores 
have a uniform protoplasmic content, which, however, ‘soon be- 
comes granular. Spores vary considerably in shape and size in 
the same sorus. While ranging from 10—28 » in length by 3.5—7 u 
in breadth they vary chiefly from 12—l6u x 4—5uz. 

The spores are produced terminally from short fertile threads 
thickly crowded together to form the fruiting sori just beneath the 
cuticle. See Plate J, Fig. 6. These fertile threads spring from 
irregular cells compacted into a stroma of greater or less extent. 
Some of these cells and threads have an olive tint even before the 
rupture of the cuticle and it is these that give the black color to 
the immature pustules. By the development of the fertile threads 
the cuticle is pushed up and, also apparently somewhat corroded, 
until it finally ruptures over the center of the sorus, and the spores 


1902. | APPLE ROTS IN ILLINOIS. 199 


which are rapidly produced one after another from the tips of the fer- 
tile threads ooze out on the surface in pinkish masses. Eventually 
spore production ceases and the whole of the sorus becomes stromatic 
tissue which has gradually assumed an olive color. The sporesin 
the meantime have been carried away or if not, those remaining, 
under moist conditions, eventually disappear through germination. 

The mycelium of the fungus runs abundantly through the 
rotten tissue of the apple and is made up, at least at first, of hya- 
line threads varying all the way in diameter from 1to7». The 
threads are more or less septate and branched and soon are pro- 
vided with granularcontents. The mycelium is also found slightly 
in advance of the rotten tissue. Near the surface by crowding be- 
tween the epidermal cells and their cuticle it gives rise to the scat- 
tered stromatic patches that form the sori. 

SPORE GERMINATION. Spores that are fresh ‘Geniinate more 
abundantly and vigorously than those that have been dried out for 
some time. VanTieghem cell cultures of fresh spores in water 
showed germination beginning inside of three hours. By the end 
of five hours some of the germ threads may be two or three times 
the length of the spore. One, two or even three germ tubes may 
emerge from a spore, coming from either end, or thesides. Usually 
the spores protrude a germ thread from either end and at the same 
time a septum is developed at the hyaline area in the center. The 
germ tubes usually grow into long, slender, slightly branched 
threads that gradually become septate and empty at their base. 
They produce a few characteristic Gleosporium spores from the tips 
of short or elongated undifferentiated branches, A peculiar feature 
is the production of oval to spherical enlarged cells on the ends of 
some of the threads and these while spore-like in appearance differ 
from the ordinary spores not only in shape but also by their deep 
brown color. They seem to be somewhat of the nature of chlamy- 
dospores as they are produced most characteristically in water or 
cultures with little nutriment. Often they send out a slender 
hyaline thread as if in germination, and on the end of this produce 
a second one. A light colored spot, apparently a germ pore, is 
usually seen at their center. In cultures containing nutriment 
one sometimes finds gradations between these bodies and the or- 
dinary colored threads and in such cases it may be that they rep- 
resent the first efforts towards the formation of the permanent 
stage of the fungus. The various phases of the germination of 
spores in water are shown in Plate I, Figs. 1-4. 

In Van Tieghem cell cultures with potato agar the germina- 
tion is much more vigorous. Two to several germ threads may be 


“ ee ee al ees ido: 


200 BULLETIN NO. 69. [February, 


developed, often two threads from the same end, with the septum 
formed at center of the spore. These germ-threads become longer, 
much more branched and retain their protoplasmic contents for a 
longer time though soon becoming septate. 

The various stages in the development of a single spore are 
shown in Figs. 5-11, Plate I. In this case the spore began to 
germinate about four hours after being placed in the medium and 

- before ten hours had sent out two germ tubes, of which one was 
more than twice the length of the spore. In less than twenty-four 
hours it had produced the much branched and septate mycelium 
partially shown in Fig. 9 and twenty-eight hours from starting 
was beginning to produce spores. The spores, as in water cul- 
tures, are produced terminally on longer or shorter branches and 
as soon as one is fully grown it falls off and another starts from 
the same ‘place. It originates as a roundish knob that rapidly 
elongates into the mature oblong spore. As it develops to its nor- 
mal size it becomes more and more constricted at its point of at- 
tachment until it is entirely cut off and falls away. The rapidity 
with which these spores can be formed is shown in Figs. 12-19, 
Plate I, three mature spores being formed from the end of the same 
branch in about seven hours. Upon germination under unfavor- 
able conditions a bunch of spores sometimes becomes bound to- 
gether by their short connecting germ tubes, as is shown in Fig. 
20 of this same plate. This is a condition similar to that some- 
times found in the old olive colored fruiting pustules of apples kept 
ina moist place, except in that case the spores are usually more or 
less olive colored. 

ARTIFICIAL CULTURES. This fungus grows very readily in 
cultural media and often pure growths may be obtained merely by 
transferring a few-spores from the top of a fresh sorus to the nu- 
trient medium in.a test tube. Cultures were made both this way 
and by the ordinary Petri dish separation method of securing iso- 

_ lated pure colonies from which mycelium was transferred to the 
test tubes. The media used for cultures were potato agar, apple 
agar, and apple agar corn meal, and each presented growths some- 
what characteristic. 

On apple agar slant tubes an evident white growth was visible 
along the needle streak at the end of the first twenty-four hours. 
By the end of the second day this growth had increased consider- 
ably and spores were being produced rather freely. Usually they 
were formed from the ends of the flocculent threads without any +* 
attempt of grouping into a sorus. Sometimes, however, where | 


1902.] APPLE ROT$ IN ILLINOIS. 208 


numerous spores have been imbedded in the medium along the 
needle streak, there were formed more compact masses somewhat 
of the nature of a sorus—there being found the stromatic layer of 
irregularly rounded cells giving rise to the densely packed fertile 
threads about twice the length of the spores produced from their 
tips. In these cases spores were produced in such numbers as to 
form pinkish masses. Soon colored threads appear among the hy- 
aline and spore formation decreases. The mycelium spreads over 
the surface of the agar to form eventually a dense felt of olive 
colored threads. See Fig. 2 a—b, Plate H. The spores soon dis- 
appear through germination and add to this growth. However in 
those cases where the spores have been produced so abundantly as 
to form the pinkish masses they remain for some time. ‘The 
mycelium is made up of branched septate threads from 7» to 1» in 
diameter. ‘The olive colored threads are sometimes seen terminat- 
ing ina hyaline part. These colored threads produce few spores 
so that with their appearance spore formation diminishes. In their 
tinted condition the threads usually have more granular contents 
than when hyaline. 

In potato agar cultures the chief difference is that, while the 
Gleosporium spores are produced somewhat more abundantly, the 
felt of mycelium on the agar is not so dense and remains white. In 
time, however, small dark spots may appear in it or sometimes on 
the edges it becomes somewhat olive tinted. See Fig. 2 d—e, Plate 
H. 

In apple agar corn meal the fungus develops most luxuriantly. 
_ At first a white growth is formed extending more or less into the 
air, but gradually the mycelium penetrates all through the med- 
ium. Gleosporium spores are formed very abundantly and often 
give a pinkish color to the places where produced most luxuriantly. 
While the mycelium is at first white, as it grows through the med- 
ium, it eventually gives this a mottled appearance due to the later 
production of olive colored threads. In time the Gleosporium spores 
disappear through germination. 

In all of these media there eventually appeared a different stage 
of the fungus which will be discussed later under the heading of 
permanent or Gnomoniopsis stage. 

ARTIFICIAL INFECTION. Artificial infection was produced both 
with picked apples and other fruits and with apples still attached 
to the trees. The fruit was not sterilized in any way as it was de- 
sired to study the disease under natural conditions, as nearly as 
possible. As the Gleosporium is a very vigorous parasite there 
was little interference by other agents of decay except in some 


202 BULLETIN NO. 69. [February, 


cases where ripe fruit was used or where the inoculate fruit was 
kept in too moist an atmosphere. Most of the experiments were 
with green apples. 

It was found that the bitter rot fungus would develop ona 
variety of fruits if spores were inserted under the epidermis by means 
of a needle. In this way there were infected apples, pears, peaches, 
grapes, and even a green tomato. The only failure was in thecase 
of a very hard, green quince. Infection was also accomplished in 
many cases merely by placing spores in a drop of water on the un- 
punctured skin or by. means of an atomizer spraying the spores in 
water over the surface of the fruit. 

Inoculation by puncture was usually evident by thie end of the 
second, and by the end of the third or fourth day often had pro- 
duced a rotten area a quarter to a half an inch in diameter, in the 
center of which the fruiting sori were appearing more or less abun- 
dantly. When the spores were placed on the unpunctured skin, if 
successful, the rotting usually began at least two or three days 
later than with the punctured fruit. The difference in the devel- 
opment of rot in punctured and unpunctured apples is shown in (a) 
and (b) of Fig. 2, Plate D. 

The effect of moisture on the production of spores and on the 
rate of development of the rot has already been described. The 
following paragraphs show some of the particular results of the . 
chief experiments. 

Experiment No. 1549. Two to four green apples each of 
Duchess, Ben Davis, Maiden Blush, Snow, and Longfield were in- 
oculated while on the trees with spores from a bitter rot apple by 
placing these under the punctured skin with a scalpel. Examined 
41 hours later and found all the apples beginning to rot around the 
punctures, forming rotten spots about % inch in diameter. At 
end of 65 hours the rotten areas averaged about % of an inch and 
the fruiting sori showed as unruptured black pustules. At end of 
ten days the rotten areas varied from % to 1% inches and all were 
‘producing spores though not with equal abundance, The Duchess 
was the most matured variety and also the worst infected. Apples 
of two of the varieties photographed ten days after inoculation are 
shown in plate F., Fig. 2a—b. | 

Experiments Nos. 1551-3. Loose green apples were inoculated 
with bitter rot spore as follows : 1551 with spores in drop of water 
on unpunctured skin of apple in moist chamber; 1552, the same 
except spores were inserted with scalpel beneath the skin; 1553, 
the same as 1552 except the apple was left in open air. At end of 
five days both 1552 and 1553 showed rotten areas about 34 inch in 


\ 


> 


1902. | APPLE ROTS In 1LLINOIS, 203 


diameter and both were producing abundant fruiting pustules but 
with this difference that on apple kept in open air they showed 
only as black unruptured sori while on apple kept in moist chamber 
they had oozed out abundance of spores in the pinkish masses. No. 
1551 did not show rot until the seventh day when it had formed a 
small spot ;4, of an inch in diameter. At end of eleventh day it 
had formed an area % of an inch and had numerous unruptured 
pustules that next day were freely oozing out spores. See Plate 
D, Fig. 2 for photograph taken on this latter date of the three 
apples. 

Experiment No. 1559. This was an experiment to determine 
if bitter rot would spread from inoculated apples to others on the 
same tree. An isolated tree of unknown variety in the old Uni- 
viersty orchard was selected and fifty apples punctured, on Aug. 3d, 
each three times with a needle containing spores. At the end of 
two weeks the rotten areas were about 3{ to 1 inch in diameter, and 
while a few of the fruiting pustules were producing spores they 
were chiefly unruptured. On August 22d, as many of the apples 
had fallen from the tree, 50 to 60 more were inoculated. Sept. 2d. 
found most of the inoculated. apples, as well as the others, fallen 
from the tree due to the very dry weather and the winds. Those 
first inoculated had rotten areas about 134 inches in diameter with 
numerous unruptured sori, while those inoculated later had rotten 
spots 4% to % of an inch without sori. When the experiment first 
began the weather was dry and very unfavorable for spore produc- 
tion and the spread of the disease, but about August 19th there were 
good rains. The variety, however, proved to be very resistant to 
bitter rot, as the rotting developed very slowly and the sori never 
fruited abundantly, and this together with the falling of the fruit 
was against the spreading of the disease. The result was that 
the rot did not spread to a single new place even on the inoculated 
fruit. Plate F, Fig. 1, shows an apple each of the first, (b) and 
second (a) inoculation photographed on September 5th. 

Experiment No. 1560. In this case three apples each of twelve 
different varieties were placed in moist chambers after being 
treated as follows: (a) had spores placed beneath the skin bya 
scalpel puncture ; (b) had spores placed in a drop of water pro- 
tected from evaporation on the unpunctured skin: (c) was an un- 
treated apple used asa check. On the third day all of the punc- 
tured apples showed rotten areas from %{ to % of an inch in di- 
ameter, but none of the others showed sigus of rot. On the fifth 
day the rotting areas were producing fruiting sori somewhat ex- 
cept in three cases, and on the twelfth day the rotten areas varied 


~ et gre - Se gi ee A ee 5 aes Eee are ee Seen eS re 
Se ae rE ee a He ral eee nae im ar & x= Py Sie, OE Poe alk eS 
é ; r . 2 jen eer AE “ Se Ore 7 : 
i ree? x5 ¥ ¥ ¥ 


S 


204 BULLETIN NO. 609. [ February, 


from 3% to 134 inches. On this day the apples with spores on un- 
punctured skin showed rotten places 4% to % of an inch in four of 
the varieties, the other eight as well as the checks being sound. 
The apples were kept under a too damp condition and this pro- 
duced on their rotten part more or less of a felt of olive colored 
mycelium. This mycelium came from the punctured places and 
from the germination of the spores, and in some cases became im- 
pure with the growth of other fungi especially with a species of 
Mycogone. In some cases where this felt had apparently re- 
mained uncontaminated there were found, about two months after 
the infection, signs of a mature stage developing in a stroma 
beneath it, and in one case there were found mature perithecia 
with ascospores similar to those produced in the artificial cultures, 
which are described later on in this paper. 

Experiment No. 1590. In this case four varieties of green 
apples were pricked each ten times around the blossom end with a 
needle containing spores and then placed undercover. A fifth or 
check apple was pricked in the same manner with a sterilized 
needJe. Three days later the inoculated apples showed rotten 
areas ;, to 4% of an inch around each of the punctures, and two 
days after this the rotten areas were beginning to merge into one 

anvuther and were forming spores abundantly in the sori. Plate E 
_ shows these and the check apple on this date. 

Experiment Nos. 1592-6. These were similar to 1590 but on 
the following fruits: hard green pear, ripe pear, very hard green 
quince, hard green peach, soft green peach. At end of three days 
the inoculations had taken effect at all of the punctures on the 
_ pears and peaches except in three cases, forming rotten areas ;; to 
i inch in diameter and rotting most vigorously on the softer pear 
and peach, especially on the latter which was producing numerous 
Gleosporium spores. By the end of the eighth day all of the 
peaches and pears were producing abundance of spores and in the 
softer ones the rotting had become very extensive. The quince 
never showed signs of rotting though kept for sometime. It evi- 
dently was too hard and green, for the most the fungus could do 
was to form a very slight growth at one or two of the punctures. 
Quinces in nature, however, are sometimes severely attacked by 
bitter rot. Plate G, Fig. 1 shows the two peaches on the fifth day 
after inoculation, the softer one (b), showing sunken areas pro- 
ducing abundance of spores, 

Experiment No. 1597. Punctured part of a bunch of green 
grapes with a needle containing spores of bitter rot and part with 
a sterilized needle and then placed the bunch in a moist chamber. 


1902. | APPLE ROTS IN ILLINOIS. 205 


A drop of liquid oozed out at each puncture and at end of second 
day the inoculated ones showed a slight growth of white threads 
at these places, and in some cases a small rotten area. At the end 
of a week many of the inoculated grapes appeared as if ripening 
and some showed numerous but chiefly unruptured sori. Plate G, 
Fig. 2, photographed thirteen days after puncturing, shows the 
sound (a) check grapes and the inoculated ones (b) with numer- 
ous fruiting sori. 

Experiment No. 1614. In this experiment spores were sprayed 
over the upper surface of a ripe pear, a green peach, a ripe crab ap- 
ple and a green apple while a check apple was merely sprayed with 
water. All were kept in a moist chamber and were sprayed sev- 
eral times with water to keep them moist. Four days later the 
pear was rotting badly but this, apparently due to its ripe condi- 
tion, was largely caused by saprophytic fungi. The green peach 
showed on the sprayed surface at least twenty sunken rotten spots, 
about 4% of an inch in diameter, the largest of which had sori pro- 
ducing spores. ‘The crab showed very many rotting areas on the 
sprayed surface, varying from very small to those % of an inch and 
often so close together as to merge into one another. Thelargest of 
these were producing spores. The green and the check apple de- 
veloped no rot. Plate D, Fig. 1, shows the condition of the crab 
apple eight days after being sprayed. 

Experiment No. 1637. This was an experiment in the Univer- 
sity orchard where eighteen varieties of apples were used. Ineach 
case a few apples were inoculated by needle punctures while others 
merely had the spores sprayed over thesurface at the stem end. It 
was not thought likely that these latter apples would develop the 
rot as they were sprayed during dry weather, when the water soon 
evaporated, and in fact none of them became infected. Most of the 
punctured places took effect and when the apples were picked eigh- 
teen days after inoculation they showed rotten areas varying from 
to 2 inches in diameter with most of them producing fruiting sori in 
varying degrees. Among those on which the rot developed most. 
vigorously were Jonathan, Snow, Maiden Blush, Ben Davis, Grimes. 
Minkler, and Dominie, though the experiment was not extended 
enough to assert that these were the most susceptible varieties. 

Experiment No. 1648 was an attempt to inoculate a green to-- 
mato by puncturing several times with a needle containing bitter rot. 
spores. At first itappeared as if this was a failure, as the rot did not. 
start. The tomato, however, began slowly to ripen and later to rot: 
around the punctures, two of which developed fruiting sori of the 
fungus. 


206 P BULLETIN NO, 69. [ February. 


Experiment No. 1584 ‘was one in which the spores of a differ- 
ent Gleosporium—one which was reported as doing considerable 
damage to Kentia palms in a Chicago greenhouse by killing the 
leaves from the tip downward and by rotting off the stems at their 
base—were used to inoculate a green apple. This apple rotted 
readily and produced numerous sori whose spores were scarcely 
distinguishable from those of the ordinary bitter rot though the 
general appearance of the rotted apple was somewhat different. 


PERMANENT OR GNOMONIOPSIS STAGE. 


ARTIFICIAL CULTURES. In practically all of the cultures that 
were made, including the petri dish separation cultures, there de- 
veloped in time an ascomycetous fungus that proved to be the per- 
manent stage of the bitter rot. This generally appeared, more or 
less matured, withim two weeks after the cultures were started and 
usually after the Gleosporium spores had chiefly disappeared 
through germination. So far as is known this is the first 
time that the permanent stage has been found. As it appeared so 
commoniy in the cultures it seems rather strange that it was not dis- | 
covered before, especially by Stoneman* who worked with cultures 
of this as well as with those of other Gleopsoriums and who de- 
scribed the new genus Gnomoniopsis as the permanent stage of 
several of these. 

In the different media used by the writer some difference in the 
luxuriance and frequency of thisstage was observed. On the apple 
agar, as has been described under the temporary or Gleosporium 
stage, the mycelium eventually formed a felt of dark olive threads 
covering the surface. It is imbedded in this and usually com- 
pletely concealed by it that the permanent stage appears. Using 
a needle to pick away the matted threads of the felt one may strike 
a harder spot which when uncovered shows as a stromatic papilla or 
cushion slightly elevated above the surface of the agar and about 
gs to 4% of an inch in diameter. Usually but few of these were 
found in atube. Sections through this stromatic cushion show it 
to be made up largely of perithecia both on the surface and en- 
tirely imbedded in it. These often appear to be in various stages 
of development and the larger ones are usually more or less united. 
See Plate J, Fig. 8. 

In the potato agar the stromatic cushions are less common and 
usually smaller. They are also less hidden from view because of 
the less dense growth that the mycelium makes on this medium 


*STONEMAN, BERTHA, A Comparative Study of the Development of some 
Anthracnoses, Bot. Gaz. 26:69-120. Aug. 1898. [Illustr.] 


1902. | APPLE ROTS IN ILLINOIS. ; 207 


and also because they are associated with an evident growth of 
colored threads that shows as a small black patch in the white 
mycelium. 

In apple agar corn meal tubes the permanent stage developed 
very vigorously. Soon after the corn meal began to have the 
mottled appearance described before small black modules appeared 
that gradually increased into conspicuous stromatic cushions about 
\% of an inch in diameter when fully grown. They developed 
scattered throughout the medium so that eventually there were to 
be found old ones at the top whose perithecia had emptied out 
their spores and lost them through germination, in the center ma- 
ture ones whose spores had just oozed out in pinkish masses on the 
surface, and at the bottom those whose perithecia still contained 
the asci and ascospores. ‘These stromatic cushions developed not 
only downward but also inward all through themedium. Plate H, 
Fig. 2c, shows a photograph of a test tube containing this me- 
dium in which a few of these stromatic cushions can be seen. 

These cushions arise from the dark olive threads becoming 
interwoven into quite dense masses forming a sort of false tissue. 
Sometimes the perithecia look as if they had been fashioned full 
size out of this. However in sections of a stroma showing all 
gradations in the formation of the perithecia what appeared to be 
the youngest condition consisted of a few hyaline somewhat poly- 
gonal cells forming a little colony in the dense mat of colored 
threads. These hyaline cells apparently increased in number, the 
outer ones becoming tinted and forming the several layers of the 
perithecial wall (or this in part may arise from the stromatic tis- 
sue) while the inner ones continued to fill this differentiated per- 
ithecium with delicate, hyaline, polygonal cells. Eventually there 


appeared toward one side a number of more elongated hyaline cells © 


and these continued to develop at the expense of the polygonal 
cells, finally forming the full grown asci each with eight asco- 
spores. See Plate J, Fig. 7 for immature stage of perithecia that 
appeared in nature on an apple. 

Sometimes in the cultures the chlamydospore-like bodies de- 
scribed before were seen and these had the color and in the irregu- 
lar forms were shaped something like the cells of the perithecial 
wall. Whether they have any special significance in the develop- 
ment of the ascosporic stage is doubtful as one may find all grada- 
tions between the quite regular spore-like forms and those that 
represent only irregular threads. 

While mature perithecia were sometimes found in the cultures 
inside of two weeks usually most of them were not so far advanced by 


Se a Le ee eS ee a 


208 BULLETIN NO. 69. (February, 


that time. In fact some of the more imbedded perithecia apparently 
never developed asci. This condition seemed to be due to the absence 
of the inner hyaline cells. The stromatic layer when full grown 
is largely made up of perithecia so that while their primary shape 
is spherical they often become more or less flattened or irregular 
by their crowding together. Apparently they developed no especial 
beak but discharged the spores by a pore or break in the perithecial 
wall. These oozed out on the surface and in the corn meal cultures 
were seen as small pinkish globules. With sufficient moisture they 
soon disappeared through germination. There were no signs of 
paraphyses. ‘The asciare quite ephemeral soon rupturing and dis- 
appearing so that it is difficult to tell an empty perithecium from 
a sterile one. Because of this temporary nature of the asci and 
ascospores it is necessary to examine the perithecia at a certain 
stage in order to find them. The germination of the spores often 
gives rise to a secondary growth of whitish threads in the cultures. 

The size of the perithecia, asci, and ascospores depends some- 
what, apparently, on the character of the cultural medium. In 
general, however, the perithecia were found to vary from 125 to 
250 » in length, while the more or less polygonal reticulations of 
their walls were about 6—14. The asci were rather numerous in a 
perithecium, the number probably depending somewhat on its size. 
Usually they had an oblong or clavate shape tapering somewhat 
to either end and often with some indication of a pedicle. See 
Plate J, Fig. 4. In those measured the size varied from 55—70 » 
in length, an average size being about 60 x9. The spores are very 
similar to those of the Gleosporium stage, in fact when discharged 
from the asci it is difficult to distinguish the two. See Plate J, 
Fig. 1a—b. Their chief difference is that the ascospores are usually 
slightly curved while the Gleosporium spores are usually straight. 
The ascospores are not quite so variable in size, ranging from 
12—22» in length by 3.5—5yin width. They are arranged in a bi- 
seriate manner in the ascus and are usually, if not always, eight 
in number. Like the Gleosporium spores, they are colorless and 
havethe central hyaline area. 

GERMINATION. The ascospores show no difference in germi- 
nation from the Gleosporium spores, giving rise to that stage. 
Like them upon germinating they usually form a septum at the 
central hyaline area. In water the germination is not very vigor- 
ous and but few Gleosporium spores are formed. The character- 
istic chlamydospore-like bodies are produced. In potato agar 
there is formed a more luxuriant mycelium with an abundance of 
Gleosporium spores. See Plate J, Fig. 1—3. 


1902. ] APPLE ROTS IN ILLINOIS. 209 


INFECTION OF APPLES. Experiments were tried two different 
times to infect apples with ascospores both by puncturing the skin 
and placing spores beneath it and by merely placing spores in a 
drop of water on the unpunctured skin. In both experiments and 
under both conditions the characteristic bitter rot of the Gleospor- 
ium stage was produced. 

On the other hand the ascosporic stage was produced from 
Gleosporium spores placed on an apple that had been sterilized in 
a pint jar in an autoclave, the treatment baking the apple and 
scattering it somewhat over the moist cotton on which it rested. 
In this case a vigorous growth of dark olive colored threads even- 
tually covered the apple. A number of Gleosporium sori were seen 
to develop at first and to give rise to pinkish masses of spores. 
Two months after inoculation the apple and cotton were removed 
from jar for examination. The mycelium had formed a very dense 
felt not only on the apple but also over the cotton where parts of 
the apple or its juice had been carried. Various stages in the de- 
velopment of perithecia were found on the apple but they were 
chiefly immature, as if the culture had not yet reached its final de- 
velopment. However, a few perithecia were found with character- 
istic ascospores. All of the Gleosporium spores had entirely dis- 
appeared through germination except some few which showed as 
the uniseptate dark olive bodies more or less connected with one 
another by short germ threads. 

PERMANENT STAGE IN NATURE. In only two cases was the 
mature permanent stage found on apples. One of these was on 
an apple that had been inoculated with the Gleosporium spores and 
being kept in a moist chamber had eventually developed a luxuri- 
ant growth of matted dark olive threads on the surface of the rot- 
ten area. Inthe other case it was found on an apple that had 
rotted in nature from bitter rot but later was kept in a moist place 
for some time. This also had developed more or less of a matted 
mycelium on the surface. With bitter rot apples that had laid 
for some time on the ground, a good many cases were found 
that seemed to indicate the beginning of this stage. Under the 
conditions that exist in nature this stage evidently develops slowly 
and ordinarily could not be expected to be found, at least in any 
abundance, before May to July of the succeeding year. As the 
writer has not had the opportunity to hunt for it at this time of 
the year he cannot state how commonly it occurs in nature. 

Apples kept in adamp place change the color of the sori as 
they become old to. quite dark olive. Examination of such sori 
shows that the dark color is due in part to the olive colored threads 


A, Se 


‘MAS. S58 Oe BR Ee Di. 
é *, nit i «Be: 


210 BULLETIN NO. 69. [ February, 


-of the stroma and in part to similarly colored spore-like bodies that 
are scattered among the normal hyaline spores. These have much 
the appearance of the Gleosporium spores except in their color and 
in the presence of the septum. They are usually found connected 
with one another by short germ tubes. It has been shown before 
that the Gleosporium spores develop a septum at germination and 
under apparently unfavorable conditions for germination, groups of 
them are sometimes connected by short germ threads; so it is 
very probable that these colored spore-like bodies are nothing more 
than Gleosporium spores that have become colored like the my- 
celium. 

It has also been shown that bitter rot apples kept under moist 
conditions, especially where the skin has been broken open, usually 
develop more or less of a mat of olive colored threads over the sur- 
face of the rotten area. This apparently comes in part from the 
germination of the Gleosporium spores and in part from the out- 
growth of interior mycelial threads. Eventually all of the Gleo- 
sporium spores disappear or show only as the two-celled colored 
‘bodies spoken of in the preceding paragraph. See Fig. 7, d, 
Plate J. The fertile threads of the sori with and after the stop- 
page of spore production become part of the stromatic layer by the 
formation of septa dividing them up into cells. These stromatic 
areas are thus gradually increased in size and become olive colored. 
From sections cut through old bitter rot apples kept in a moist 
place it seems probable that the permanent stage is developed in 
the stromata of the old Gleosporium sori or in those that did not 
mature to produce this stage and perhaps even in the matted 
growth of threads that develops entirely on the exterior. This ex- 
terior growth of threads at least serves during the winter as a pro- 
tective covering for the fertile cells beneathit. In nature the stro- 
matic cushions are apparently not so prominent as in artificial 
cultures and the perithecia are no doubt few in number and never 
deeply imbedded. Plate J, Fig. 7, shows a cross section of an old 


bitter rot apple having two well advanced perithecia and ap- 


parently a very young one. 
CLASSIFICATION. In attempting to classify this permanent 
stage the writer found considerable difficulty as it did not agree 
with any of the genera given in Saccardo’s Sylloge Fungorum. 
Itseems, however, to come under the new genus described by 
Stoneman to which reference has already been made. Ina few 
minor characters it does not coincide with the description given for 
Gnomoniopsis but these are such as might arise from a description 
based partially on the stage as produced on artificial media or the 


Tit aaah Lin p< a a 


1902. ] APPLE ROTS IN ILLINOIS. 211 


insertion of characters not really generic. As the bitter rot fungus 
is merely the summer stage in the life cycle, it becomes necessary 
to re-name it under the genus of its permenent stage. As has been 
shown by Southworth* the bitter rot stage has received a number 
of names. Probably the species described in 1856 by Berkeley’ as 
_Gleosporium fructigenum was the first name applied to it and this 
is the one that is now in common use. ‘The proper name then for 
the fungus as now understood is Guomoniopsis fructigena (Berk.) 

SCIENTIFIC DESCRIPTION. ‘The generic characters of Gnomon- 
iopsis, as modified somewhat by the writer’s investigations, to- 
gether with the description of the species causing bitter rot may be 
given as follows: 

GNOMONIOPSIS, Stonem. Perithecia membranaceous, dark 
brown, spherical to flask shaped, often rostrate, sometimes evi- 
dently hairy, cwespitose or more or less compound and immersed in 
a stroma with which they often form an evident hard cushion; 
asci oblong to clavate, often fugacious, aparaphysate; ascospores 
hyaline, apparently eight, distichous, oblong, usually slightly 
curved, unicellular. Permanent stage of Gleosporium-like. fungi. 

Gnomontopsis fructigena (Berk.) Clint. n. n. permanent stage 
developing on decayed pomaceous fruits; forming stromatic cush- 
ions (often concealed by dark olive mycelial felt), which contain 
immersed and more or less compounded, subspherical perithecia; 
asci subclavate, often slightly pedicellate, fugacious; 55—70» in 
length, ascospores alantoid, with evident central hyaline area chiefly 


12—22x3.5—5. Gleosporium stage causing rotting of pomaceous ~ 


fruits; sorismall, developing more or less in concentric circles, usually 
soon rupturing and oozing out spores iu small pinkish masses ; 


spores hyaline, chiefly oblong, unicellular, with evident hyaline 


areas when fresh, 10—28 x 3.5--7 but chiefly 12—16 by 4—5Su. 


ee E.A. Ripe Rot of Grapes and Apples. Journ. Myc. 6:164- 
73. 1891. 
2BERKELEY, M.J. Gleosforium fructigenum,n.s. Gard, Chron. 1856: 245. 


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i BULLETIN NO. 60. [ February, 


EXPLANATION OF ILLUSTRATIONS. 


Plate A, Fig.1. Apple showing sun burn. 


Plate A, Fig.2. Apples showing rot started at injured places produced by birds 
and worms. 


Plate B, Fig.1. Apples showing fruit blotch. (a-b) in the earlier, and (c) in the 
later stage. 


Plate B. Fig.2. Apples showing stages (a-d) in the development of black rot, (a) 
not yet having formed fruiting conceptacles, (d) with abundance 
of them containing mature spores. 

Plate C,Fig.1. Apple showing very young state of bitter rot, with many colo- 

é ; nies scattered over its surface. 


Plate C, Fig.2, Apples showing different stages of bitter rot in which colonies 
have attained considerable size and have developed numerous 
fruiting sori; (a, c) developed from single and (b) from several 

‘. colonies. 
Plate D,Fig.1. Artificial infection of bitter rot produced on ripe crab apple, 
kept in moist chamber, by spraying with water containing spores 
Hae of bitter rot. Sprayed Aug. 23d and photographed Aug. 31st. 

Plate D,Fig.2. Artificial infection of three green apples under different condi- 
tions: (a) spores placed in drop of water on the unpunctured sur- 
face and apple kept in moist chamber; (b) spores placed under 
the skin by needle puncture and apple kept in moist chamber ; 
(c) same as (b) but apple kept in open air; (a) and (b) have nu- 
merous sori producing spores, while in (c) they remained as un- 
ruptured pustules. Apples treated July 25thand photographed 

Aug. 6th, 

Plate E. - Four varieties of green apples (a-d) each punctured ten times 
around the blossom end with a needle containing bitter rot spores 
and kept in a damp chamber ; (e) check apple merely punctured 
with sterilized needle. Apples punctured Aug. 16th and photo- 
graphed Aug. 2Ist. 


Plate F, Fig.1. Apples of an unknown variety inoculated with bitter rot, by 
needle punctures. while onthe tree ; (b) inoculated Aug. 3d, and 
(a) Aug. 22d, both being photographed Sept. 5th. This proved to 
be a variety very resistant to bitter rot; (a) developed no sori 

: while in (b) they were chiefly immature. 

Plate F, Fig. 2. Apples inoculated with bitter rot, by scalpel pain eiiies while 
still on the tree ; photographed ten days after inoculation. These 
two varieties were quite susceptible to bitter rot; they show the 
fruiting sori and the central sunken areas. 


Plate G.Fig.1. Hard (a) and soft (b) green peach punctured ten times with a 
needle containing spores from bitter rot apples and then kept in 
a moist chamber, (b) producing abundance of spores from the 
fruiting sori. Punctured Aug. 16th and photographed Aug. 2Ist. 

Plate G, Fig.2. Green grapes (b) each punctured once with a needle containing 
spores from bitter rot apple and then placed in moist chamber; 
(a) check grapes, merely punctured with a sterilized needle. 
Punctured Aug. 17th and photographed Aug. 30th, at which time 
inoculated grapes were covered with sori producingspores. 


ict isk CRW ay 15d 2 Re ae 


1902. } 


Plate H. Fig-1. 


Plate H, Fig. 2. 


Plate I. 


“\ 
APPLE ROTS IN ILLINOIS. 213 


Apples showing development of bitter rot under different condi- 
tions of moisture; (a) kept in open air, fruiting pustules remain- 
ing unruptured ; (b) kept under a bell jar, fruiting pustules pro- 
ducing abundance of spores ; (c) kept under bell jar with moist- 
ure, fruiting pustules producing spores and felt of mycelium 
growing over the surface. Pin heads mark the boundary of the 
rot when treatment began on July 26th; photographed Aug. 6th. 


Test tube cultures ofthe bitter rot fungus on different media ; (a) 
front and (b) back view of culture on apple agar, the fungus 
making a dark growth on this medium ; (c) culture in apple agar 
corn meal, showing a few stromatic cushions of the permanent 
stage ; (d) back and (e) front view of culture on potato agar, the 
mycelium forming a white growth on this medium. 


Bitter rot: (a) spores; (b) germ threads on mycelium; (c) chlamy- 
dospore-like bodies. 


Fig. 1-4, showing germination of bitter rotsporesin water in Van Tieghem 


cells. Fig. 1, condition of spores when first placed in water, 11 
a.m., Aug. 30th. Fig. 2, various stages of spore germination at 
4p. m., Aug. 30th. Fig. 3, stages of germination at Io a. m., Aug. 
31st; 3', Showing full length-of germ threads of two spores less 
highly magnified. Fig. 4, general condition of the mycelium 10 
a. m.. Sept. 2d, producing chlamydospore-like bodies (c) and a 
few Gleosporium spores (a). 


Fig. 5-11, showing germination of a single spore (5) in potato agar in Van 


Tieghem cell. Fig. 5, condition of spore 10:30 a. m., Aug. 16th 
when spore was first placed in potato agar. Fig. 6, 3 p. m., just 
after spore began to germinate. Fig. 7, condition at 5:30 p. m., 
Fig. 8, condition at 8 p.m. Fig.9, condition at 9 a.m., Aug. 17th, 
less highly magnified to show extent of mycelium at this time. 
Fig. 10, central part of mycelium of Fig. 9. Fig. 11, partial view 
of mycelium at 2:30 p. m., showing formation of Gleosporium 
spores. ‘ ‘ 


Fig. 12-19, showing manner and rate of production of Gleosporium spores in 


potato agar in Van Tieghem cells. three spores being formed in 
less than eight hours. Fig. 12, condition at 9a.m.; Fig. 13, at 
9:05 a.m.; Fig. 14, at 10:30 a. m.; Fig. 15,at I11a.m.; Fig. 16, 
at 12N; Fig. 17, at 3:00 p. m.; Fig. 18, 3:30 p.m.; Fig. 19, at 
4:10 p. m,: 


Fig. 20, showing spores that had been produced in Van Tieghem cell 


Plate J, Fig. 1. 


uniting by short germ tubes after manner so common with spores. 


in old sori on the apples kept in moist place. 

Ascospores from permanent stage of bitter rot fungus; (a) typical 
spores ; (b) spores of somewhat unusual shapes ; (c) germinating 
spores after 16 hours in water in Van Tieghem cell; (d) germina- 
ting spores at end of 40 hours. 


Fig. 2-3, germination of the ascospores in potato agar; (a) spores; (b) germ 


threads. Fig. 2, germination at end of 16 hours, a’ being less 
highly magnified. Fig. 3, part of mycelium showing spore pro- 
duction at end of 41 hours, 


214 BULLETIN NO. 69. [ February, 


Fig. 4, showing two asci with ascospores of the permanent stage of bit- 
ter rot, also one free ascospore. Spores somewhat displaced out 
of their distichous arrangement. ' 

| Fig. 5. showing rather diagrammatic drawing of a section througha 

3 young bitter rot fruiting sorus on apple; (a) parenchyma cells of 

apple; (b) cuticle of apple; (c) subhymenial layer of fungus cells; 

“(d) fertile threads of fungus ; (e) spores. 

4 Fig. 6, showing character of fertile cells of sorus with jeu Gleo- 
sporium spores. 

Fig. 7, showing section through surface of an old bitter rot apple on 
which the permanent stage is developing ; (a) parenchyma cells; 
(b) cuticle ; (c) fungous threads of the felt; (d) old, dark colored, 

. uniseptate Gleosporium spores. Two perithecia well advanced, 

3 < one showing young asci starting at its base; also a very young 

- stage of a perithecium. 

Fig. 8, showing diagrammatic drawing of a section through part of a 
stromatic cushion of the permanent stage of bitter rot. This is 
from a culture grown on apple agar. It shows various sizes of 
the perithecia (a). ; 


Fig. 5, 7, 8 less highly magnified than the other iiagthas 


1902. ] APPLE ROTS IN ILLINOIS. 215 


Plate Al) 


BULLETIN NO. 69. 


1902. ] APPLE ROTS IN ILLINOIS. 


————— 


Fig. 1 


BULLETIN 


NO. 


[ February,. 


Plate D, | 


i 


APPLE ROTS IN 


ILLINOIS, 


r< eS }.~ ae 2 x 
> «e Ne >» i) s P (50a ee tee ee ee a 


| February, 


“Plate F. 


1902 ] APPLE ROTS IN ILLINOIS, 22k 


BULLETIN 


223 


APPLE ROTS IN ILLINOIS. 


1092.] 


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